Problem: In the right triangle shown, $AC = 3$ and $AB = 10$. What is $BC$ ? A C B 3 ? 10
We know $a^2 + b^2 = c^2$ We want to find $a$ ; let $b = 3$ and $c = 10$ So $a^2 = c^2 - b^2 = 10^2 - 3^2 = 91$ Then, $a = \sqrt{91}$.